Sound-reproducing device



Dec. 7,1926. Y 1,609,540

R. H. GODDARD ET AL SOUND REPRODUCING DEVICE Filed June 18. 1921 Patented Dec. 1, lens.

UNITED STATES r 1,009,540 PATENT OFFICE.

ROBERT E. GODDARD, OF WORCESTER, KABSA OHUSETTS. AND LOUIS '1. E. THOMPSON, OI KALAKAZOO, MICHIGAN.

SOUND-PRODUCING DEVICE.

Application flea June 18,

This invention relates to apparatus ferreproducing sound andparticularly to an 1mproved diaphragm or amplifier adapted for y use with onographs or other similar ma-,

5 chines.- 'l he usual reproducing d aphragm is of considerable size. When sounds are reproduced by such a diaphragm additional audible notes or overtones are developed which depend in a general way upon the in size, shape and material of the diaphragm Other overtones-re resent the natural frequency of the horn, ox or air chamber with which the diaphragm is associated. These overtones alter the character of the soundreproduced by the diaphragm and detract from its quality.

It is the general object of our invention to rovide a novel form of sound reproducm'gap ratus by the used which t ese objectiona 1e overtones may be avoided and by which. the purity and clearness of the original sound may be closely reproduced. In the preferred embodiment of our invention we employ a' sound reproducing de- 26 vice comprismg a large number of relatively small vibrating elements. The natural notes or overtones of these small vibrating elements and their associated air chambers, if any, are so high that they are'not audible to 80 the human ear.

, These elements are caused to vibrate in union by electrical or othersuitable means. .The volume of sound produced by a single such small element is corresponding! small as but the desired loudness or volume 0 sound is attained by egreatly increasing the number of vibrating ements. Provision mayalso be made for directing the sound ins definite direction ifso desired. w The construction and operation of 7 our improved reproducing apparatus may be understood by reference to the accompanyin drawings, in which- P 'g. 1 is'a proved reproduc' ap ratus, and

' Fig. 2 is a dets' sectional elevation.

In the form shown in the drawings, the relatively sma vibrating elements com rise parts of continuous thin metallic ribbons 10 which are supported on knife edges 11 and which aree'gr erahly tightly stretched over the knife in any convenient manner as b turn-hue es 10. Each portion of each' ribbon between ad'acent knife edges constiie tutes eeeparate vi rating element by which definite direction and for this plan of one form of our int- 1921. Serial No. 478.849.

tinned centrally beneath each separately vibrating element of the ribbon 10. A wire 14 is wound around each bar 12, the winding being reversed between each pair of projections 13.

.When a current of electricity is sent through the wire 14 the bars 12 are thus divided into a series of-electromagnets, the adjacent projections 13 being of opposite polarity. A separate electromagnetic circuit is thus provided between each pair of rejections and includes the portion of the ar between the projections and also the portion of the steel ribbon extending from one projection to the other and closely adjacent thereto.

n is frequently desirable to direct the sound from the vibrating elements in a urpose we may provide a cellular or gridike framework 15 supported adjacent the ribbons 10. This frame-work rovides small air chambers or cells 16 su stantially corresponding in area and position to each vibrating ribbon element. The upright walls of the cells direct the air in the desired direction.

' By using this cellular structure comprising a large number of air chambers in lace of the usual box or horn we avoid a objectionable overtones associated with the usual large horn or air chamber. The overtones of the chambers 16 are of too high frequency to be detected by the ear.

Any suitable provision may be made for supplying avariable electric current to the wire or wires 14. One form of apparatus suitable for supplying such current 1s shown in Fig. 1 and comprises an electric circuit 20 adapted to carry a small variable current of electricity such as may be received from a phonograph record or from a telephone transmitter. The current in the circuit 20 is conducted to an amplifier of suitable form, which may comprise a vacuum tube 21, a

plate 22, a filament 23, a grid 24, a filament heating battery 25 and a high tension battery 26. The current is first increased in voltage and then transformed and increased in volume by a transformer 27 It may be still further increased by the use of one or more additional amplifiers 28 and transformers 29. By this or similar ap status the slight variable current taken cm a. phonograph or telephone circuit ma be increased to an amount suflicient to e ectively m agnetize the bars 12 and projections 13 and to cause such vibrations of the ribbon elements as will produce the desired volume of sound.

We have also indicated in Fig. 1 a form of phonograph record and record-engaging element by which a variable current may be developed direct from the phonograph record. or this purpose the record is formed upon a steel disc 30 having a spiral rid 31 formed thereon. The record is forlm by variably magnetizin the difl'erent parts of the ridge 31, and tfie reproducing element engaging the disc comprises two ma ets 32 and 33 having their e iec'es touc g the o posits sides of t e -shaped ridge 31.

see magnets are connected in series in the circuit 20, and the small variable current induoed by the va 'n magnetism of the ridge 31 asses throu t e amplifier 21 and such ad itional amp fiers 28 as may be necessary, until the current is of such volume that it will effectively to etize the electro-magnets having the prqections or pole ieces 13. These magnets thereupon cause, of the steel ribbon sections between the supports 11 to vibrate in unison and with the same amplitude, thus producing a small volume of sound from each element, free from audible overtones. The total volume of sound may be increased as desired by adding more v1- brating elements, the number of which may be extended indefinitel Having thus descri ed our invention it will be evident that chan es and modifications may be made therein those skilled in the art within the spirit an scope of our invention as set forth in the claims, and we do not wish to be otherwise limited to the details herein disclosed but what we claim 1. A sound reproducing device comprising a unitary resilient vibrating member subdivided by engagement of contactin ele ments therewith into a large number 0 relatively small connected vibratin portions each reproducing the same soun and each of a len th so short that its natural tones are inaudible.

2. A sound reproducing device comprising a unitary resilient vibrating member subdivided by engagement of contacting elements therewith into a plurality of relatively small connected vibrating portions each of a length so short that its natural tones are inaudible, and means for separately vibrating each such portion, all of said ortions being vibrated simultaneously an with equal amplitude.

3. A sound reproducing device comprising a nnita resilient vibrating member subdivided by engagement of contactin ele' ments therewith into a large number 0 relatively small connected vibrating portions each of a len th so short that its natural tones are inau ible, electrically operateddevices for vibrating all of said portions simultaneously, means to produce small variable currents of electricity, and amplifying devices interposed between said means andsaid electrical] operated devices whereby an efiective varia le current is supplied to said devices.

4. A sound reproducing device comprising a steel ribbon, a plurality of spaced supports for said ribbon efi'ective to sub-divide said ribbon into separately vibrating connected portions. each of a len b so short that its natural tones are inau ible, and magnetic means to separately vibrate the portion of said ribbon between each pair of supports.

5. A sound reproducing device comprising a steel ribbon, a plurality of spaced su ports for said ribbon effective to sub-dividi: said ribbon into separately vibrating connected portions, means to stretch said ribbqn tightly over said supports to render its natural tones less audible, and ma net'io means to vibrate the portions of said ribbon between the pairs of supports.

6. A sound reproducing device comprising a sounding box of cellular construction, a unitary member sub-divided by engagement of contacting elements therewith into relatively small connected vibratinv portions, each subdivided portion thereof laeing positioned at the back of a cell in said box, and means to vibrate all of said ortions in unison.

7. A sound repro ucin device com rising a unitary vibrating mem er sub-divi ed by engagement of contacting elements therewith lnto a large number of relatively small connected vibrating portions, means to vibrate all of said portions simultaneously, and a plurality of relatively small air chambers, one of said chambers being associated with each small vibrating portion, whereby the direction of the sound waves may be controlled.

In testimony whereof we have hereunto affixed our signatures.

ROBERT H. GODDARD. LOUIS T. E. THOMPSON. 

